Heat detecting cable and connector assembly



8 5 L. v. HEBENSTREIT 2,802,924

v HEAT DETECTING CABLE AND CONNECTOR ASSEMBLY Filed Nov. '2, 1953 ATTORNEY HEAT DETECTING CABLE AND CONNECTOR ASSEMBLY Lester V. Hebenstreit, Bloomfield, N. J., assignor to Specialties Development Corporation, Belleville, N. J., a corporation of New Jersey Application November}, 1953, Serial :No. 389,702 '2 Claims. ((21. 201- 63 The present invention relates ,to heat and ,flame detecting devices; and, more particularly, is concerned with improvements in heat detecting cables and connector assemblies for such cables, .wherein electrically conductive elements are separated'by a mass of material which acts as an insulatorat a given temperature and ,is adapted to be rendered electrically conductive at another temperature.

Heretofore, it has been customary to construct such cables by having the mass of material surround two electrically conductive uninsulated wires and maintain them .spaced apart, and inserting. the mass in a bendable tube adapted to enclosethe same.

A connector was secured to each end of the cable structure which included two pins each connected to one of the wires respectively. Since the ends of the tube must be hermetically sealed to prevent moisture from entering the mass and changing the electrical characteristics thereof, considerable difficulty and expense were encountered in providing such a seal in connection with a two pin connector because special structure and seals had to be employed. An example of such a connector may be found in my copending application for United States Letters Patent, Serial No. 255,483, filed November 8, 1951, now Patent No. 2,678,366.

It also has been proposed to avoid such complications by utilizing a cable comprising a single wire embedded in the mass of material, and a tube surrounding the mass and serving as a second wire in electrical connection with a simplified connector. However, the difliculty with such cables is that the mass is not in good electrical contact with the inner wall of the tube throughout the length thereof, whereby, when heat or flame is concentrated on a portion of the cable where the contact between the mass and tube is imperfect, such heat or flame condition will not be detected quickly, accurately and uniformly. Consequently, such single wire assemblies were considered unreliable and were not approved.

The present invention aims to overcome these difliculties by providing a heat or flame detecting cable which has the accuracy and reliablility of a two wire assembly but yet requires a connector which is as simple and inexpensive as one utilized in connection with single wire assemblies.

Accordingly, an object of the present invention is to provide an improved flame or heat detecting cable and connector assembly.

Another object is to provide such an assembly which is accurate and reliable and yet is simple and economical in construction.

A further object is to provide such an assembly which can readily withstand the rough usage to which it may normally be subjected without requiring replacement or repair.

Other and further objects of the invention will be obvious upon an understanding of the illustrative embodiment about to be described, or will be indicated in the appended 2,802,924 Patented Aug. 13, 1957 2 claims, and various advantages not referred to hereinwill occur toone skilled in the art upon employment of-the invention in practice.

In accordance with the present invention, the foregoing objects are accomplished by providing a heat or fiamedetecting cable which comprises two electrically conductive, uninsulated wires which are substantially coextensive in length and are spaced apart fromeach other; a mass .of material surrounding-the wires and maintaining them in spaced apart relation, the material acting as an insulator at a given temperature and being adapted to berendered electricallyconductive at another temperature; and an electrically conductive tube surrounding said mass, one of the wires being electrically connected to the tube adjacent at least one end thereof, but preferably at both ends thereof. Anend connector for the cable includes an electrically conductive body secured to the tube adjacent the end thereof in electrical connection withthe tube and the last mentioned wire.

A preferred .embodiment of the invention has been chosen for purposes of illustration and description, and is shown in-the accompanying drawing, forming a part of the specification, wherein:

:Fig. 1 .is ,an. enlarged fragmentary longitudinal sectional view of a cable and connector assembly in accordance with the present invention.

Fig. .2 is a furtherenlargedsectional view taken along the line 2- '2 on Fig. 1.

Referring to the drawing in detail, there is shown a heat or flame detecting cable 10 and an end connector 11 for the cable.

The cable 10 comprises two electrically conductive uninsulated wires 12 and 14, which are substantially coextensive in length and are spaced apart from each other; a mas or core of ceramic-like, thermistor material 15 surrounding the wires and maintaining them in spaced apart relation; and an electrically conductive bendable tube 16 surrounding the mass to which one of the wires is electrically connected in the manner described hereinafter.

The mass of material 15 acts as an insulator at a given temperature and is adapted to be rendered electrically conductive at another temperature. This material may be of the type disclosed in United States Patent No. 2,495,867, dated January 31, 1950.

The connector 11 generally comprises an electrically conductive tubular body 17 in connection with one of the wires and the tube 16, and an electrically conductive pin or rod 19 extending axially within the body and centrally located therein but insulated therefrom and in electrical connection with the other of the wires. The cable and connector assembly in this manner provide two wires across which electrical contact can be made when the material 15 becomes conductive to establish a circuit. Since the tube 16 and the wire 12 in electrical connection with the tube serve as one side of the circuit, current can flow between the wire 14 and these elements when the material 15 is rendered conductive.

The tubular body 17 comprises a metallic sleeve 20 formed with an aperture wall 21 at about the middle thereof wherein a mass of material 22 is positioned, such as electrical glass, which supports the pin 19 and, if desired, forms a hermetic seal between the pin and the wall while insulating the pin therefrom; and a metallic closure 24 having a tubular section 25 through which the cable 10 extends and having a flange 26 and a collar 27 fitting into the sleeve 20 and hermetically sealed thereto by soldering, welding or brazing the flange to the external end of the sleeve.

While the wire 12 for example may be electrically connected to the tube 16 in any suitable manner, a convenient way of accomplishing this is to so connect the wire 12 by the tube 16. If desired, this end of the cable tube may be further sealed by a glass head 31 through which the wires 12 and 14 extend.

Only one end of the cable and connector assembly is shown herein for purpose of illustration, but it will be understood that the end not shown may be identical therewith.

From the foregoing description, it will be seen that the present invention provides a novel and useful cable and connector assembly of the heat or flame detecting type. The cable has all the advantages of a two wire cable without requiring a two wire connector. The connector shown herein is formed of simple, durable parts which can be manufactured an assembled in a rapid and economical manner.

As various changes may be made in the form, construction and arrangement of the parts herein, without departing from the spirit and scope of the invention and without sacrificing any of its advantages, it isto be understood that all matter herein is to be interpreted as illustrative and not in any limiting sense.

I claim:

1. A heat detecting cable and connector assembly comprising a connector including a tubular electrically conductive section formed with a central bore, a contact element in electrical connection with said section, and a second contact element supported by said first mentioned contact element and electrically insulated therefrom; a heat detecting cable including an electrically conductive bendable tube extending through said bore, a core of thermistor material within said tube, and a pair of uninsulated electrically conductive wires coextensive with each other and embedded in said core in spaced relationship from each other and said tube with the end of each wire extending outwardly of said tube, the end of one of said wires being electrically connected to said second contact element; and a mass of electrically conductive material adjacent said tube and on a portion of said tubular section defining said bore, the end of said other wire being embedded in said mass to electrically connect the same to said tubular section and said first mentioned contact in electrical connection therewith.

2. An assembly according to claim 1, wherein said tube extends outwardlybeyond said bore and said mass of electrically conductive material extends completely about said tube to provide an annular seal for said bore at the zone where said tube extends outwardly beyond the portion of said tubular section'defining said bore.

References'Cited in the file of this patent UNITED STATES PATENTS 1,026,238 Andersen May 14, 1912 2,594,921 Hansard Apr. 29, 1952 

